Dynamometers have been used for many years to plot load versus position on reciprocating well pumps. Electronic dynamometers have more recently been introduced and employ a load cell and a position-variable potentiometer as input to an x-y plotter as disclosed in my co-pending patent application Ser. No. 06/089,844, entitled Control Circuit for Shutting Off the Electrical Power to a Liquid Well Pump. The resulting plot of position (x-axis) versus load (y-axis) is used to determine the amount of stress on the rods connecting to the pump; the amount of torque on the pumping unit gearbox; and for performing time related Fourier analysis in order to gain information about the downhole pump. Computer programs have been developed to perform these calculations. The traditional method for inputting data to these programs has been to choose data points from the plot and manually enter the data points into the program.
The present invention accepts the analog voltages from the load cell and position transducer as each is input into the x-y plotter and digitizes each signal and stores the data on an electronic digital memory. Control circuitry insures proper start/stop timing. Once the data is stored, the present invention allows the digital data to be replayed through a digital to analog converter onto the x-y plotter so that the operator can verify that the recorded data is correct. The present invention allows the memory card to be removed once the data is recorded and a second memory card inserted so that multiple recordings can be made on a single field trip. The present invention allows the memory card to be attached to a transmitting device, which may or may not be separate from the recording device. The transmitting device accepts the memory data and adds the necessary control characters and transmits the data serially at a rate acceptable to a computer.